【Objective】 To explore the effects of nerve growth factor （NGF） on bladder function and axon injury repair in rats with traumatic spinal cord injury （t-SCI） so as to explore its molecular mechanism. 【Methods】 Traumatic spinal cord injury model was constructed in 30 male SD rats by modified Allen’s beating method. The rats were randomly divided into sham-operation group， injury group and NGF group， with 10 rats in each group. We used the BBB score to observe the motor function of the rats’ hind limbs before and after the operation. The BL-420 biometer experimental system detected the urodynamics. Six anterior roots of the left lumbar taken from the distal end of the anastomosis were stained with toluidine blue， and the number of myelinated axons was counted. We used HE to stain rat bladder tissue， TUNEL to stain the rats’ severely injured spinal cord， and observed the spinal cord apoptosis rate. Western blotting was used to detect the protein expressions of Raf-1， p-MEK-2， MEK-2， ERK1/2， and p-ERK1/2 in spinal cord tissue. 【Results】 The BBB score results showed that there was no difference in the scores of the sham-operation group， the injury group and the NGF group before the operation. After the operation， the scores of the injury group and the NGF group were significantly lower than those in the sham-operation group （P<0.05）. The maximum detrusive pressure and the number of axons were significantly lower in the injury group than in the sham-operation group and the NGF group （P<0.05）， but the residual urine volume and bladder cell apoptosis rate in the injury group were notablely higher than those in the other two groups （P<0.05）. HE staining results showed that bladder edema in the injury group was severe and the detrusor muscle structure was loose， while the NGF group had reduced bladder injury. Western blot results showed that the protein ratio of p-ERK1/2/ERK1/2 and p-MEK-2/MEK-2 and the expression of Raf-1 in the injury group were significantly higher than those in the sham operation group and NGF group （P<0.05）. However， there was no significant difference between the sham operation group and the NGF group in maximum detrusive pressure， the number of myelin axons， residual urine volume， bladder cell apoptosis rate， or protein （P>0.05）. 【Conclusion】 NGF may hinder the conduction of MAPK/ERK pathway， thereby affecting the repair of axon damage and improving the bladder function of t-SCI rats.

Studies on coat protein I (COPI) have contributed to a basic understanding of how coat proteins generate vesicles to initiate intracellular transport. The core component of the COPI complex is coatomer, which is a multimeric complex that needs to be recruited from the cytosol to membrane in order to function in membrane bending and cargo sorting. Previous structural studies on the clathrin adaptors have found that membrane recruitment induces a large conformational change in promoting their role in cargo sorting. Here, pursuing negative-stain electron microscopy coupled with single-particle analyses, and also performing CXMS (chemical cross-linking coupled with mass spectrometry) for validation, we have reconstructed the structure of coatomer in its soluble form. When compared to the previously elucidated structure of coatomer in its membrane-bound form we do not observe a large conformational change. Thus, the result uncovers a key difference between how COPI versus clathrin coats are regulated by membrane recruitment.
ADP-Ribosylation Factor 1 ; chemistry ; metabolism ; Animals ; Coatomer Protein ; chemistry ; metabolism ; Cytosol ; chemistry ; metabolism ; GTPase-Activating Proteins ; chemistry ; metabolism ; Humans ; Membranes, Artificial ; Rats